1. Field of the Invention
The present invention relates to heater devices, and more particularly to low profile heater devices. More specifically, the present invention relates to a low profile heater device used in injection molding processing and a related method of manufacture thereof.
2. Prior Art
In a mold injection process, it is important to maintain a resin in a molten state as it flows from a nozzle of an injection molding machine through a hot runner nozzle and into a mold cavity space, wherein the resin is allowed to cool and form an injection-molded article. To maintain this molten state, a heating device is usually provided adjacent to the hot runner nozzle. A typical prior art heating device is found in U.S. Pat. No. 5,051,086 to Gellert which discloses an injection molding nozzle having several layers of steel and ceramic insulating material that surround a coiled electrical heating element. During fabrication, the coils of the heating element are wound around the body of the nozzle and alternating layers of an insulation material are plasma sprayed over the coil to form a thin layer which provides for a completely integral structure. However, fixing the heating element of Gellert requires that the entire nozzle be replaced because of the integral nature of the device.
Other patent references, such as U.S. Pat. No. 5,973,296 to Juliano et al., disclose a tubular heater having a metallic substrate that has a dielectric film layer and a resistive thick film layer applied directly to the exterior cylindrical surface of the tubular substrate by a method of precision fine film printing. Unfortunately, such a method of manufacture does not address heating devices where a thick layer of ceramic insulating material is required to surround the heating element during fabrication.
Therefore, there appears a need in the art for a heater device that is attachable to a hot runner nozzle for maintaining resin in a molten state. Additionally, there appears a need in the art for a method of fabricating a heater device having a thick insulating material for encasing an electrical heating element.